If the heat mat area on the side of the tank is too hot i would imagine the frogs wouldn't chill there. here's something i've noticed with my Exo terra heat mat that i have on the side of my tank. I have the small rainforest version (8" x 8") just by moving my temp probe around i have found that you really only get heat right on the glass where the mat is. My tank is only a 10 gallon vertical and the temp difference from the side right where the heat mat vs the opposite where there is no heat mat is around 5 degrees or so